Arrival direction estimation apparatus

1. An arrival direction estimation apparatus comprising: an antenna in which a plurality of antenna elements are symmetrically arranged centering on a given reference position or a reference line and which receives signals by the plurality of antenna elements; a complex digital signal converting means which converts the signals received by each antenna element of the antenna to complex digital signals; a real number correlation matrix calculating means which calculates a real number correlation matrix expressing correlation among the plurality of antenna elements of the complex digital signals; a real number weight matrix calculating means which calculates a real number weight matrix used for calculating a spectrum based on the calculated real number correlation matrix; a spectrum calculating means which calculates the spectrum based on the calculated real number weight matrix and a previously prepared real number matrix used for calculating the spectrum; and a spectrum peak detecting means which detects a direction with a peak value with the use of the calculated spectrum, wherein the spectrum calculating means includes a real number matrix storing means which stores the real number matrix, a multiplying means which multiplies part of elements of the real number matrix stored in the real number matrix storing means by part of elements of the real number weight matrix, a result storing means which stores a processing result of multiplication by the multiplying means, a calculating means which performs at least one or more processing of matrix element inversion processing and matrix element sign change processing for the processing result stored in the result storing means, an adding means which adds a processing result by the calculating means, part of the processing result stored in the result storing means, and part of the elements of the real number weight matrix, and a spectrum calculating means which calculates the spectrum with the use of a processing result by the adding means.

2. The arrival direction estimation apparatus according to claim 1 comprising: an arrival direction calculating means which estimates an arrival direction of the signals based on spectrum results at the direction detected by the spectrum peak detecting means and peripheral directions thereof.

3. The arrival direction estimation apparatus according to claim 1 wherein the spectrum calculating means comprises: the real number matrix storing means which stores the real number matrix; the multiplying means which multiplies the part of the elements of the real number matrix stored in the real number matrix storing means by the part of the elements of the real number weight matrix; the result storing means which stores the processing result of multiplication by the multiplying means; the calculating means which performs at least one or more processing of the matrix element inversion processing and the matrix element sign change processing for the processing result stored in the result storing means; the adding means which selectively adds elements from the group including the processing result by the calculating means, the part of the processing result stored in the result storing means, and the part of the elements of the real number weight matrix; and the spectrum calculating means which calculates the spectrum with the use of the processing result by the adding means, and wherein the adding means stores a given processing result by itself in the result storing means.

4. The arrival direction estimation apparatus according to claim 1 , wherein the real number matrix storing means stores only the part of the elements of the real number matrix.

5. The arrival direction estimation apparatus according to claim 1 , wherein the spectrum calculating means calculates the spectrum by using a multiplication result of elements of the vectors indicating directivity of the antenna.

6. An arrival direction estimation apparatus comprising: an antenna in which a plurality of antenna elements are arranged and which receives signals by the plurality of antenna elements; a complex digital signal converting means which converts the signals received by each antenna element of the antenna to complex digital signals; a correlation matrix calculating means which calculates a correlation matrix expressing correlation among the plurality of antenna elements of the complex digital signals; a weight matrix calculating means which calculates a weight matrix used for calculating a spectrum based on the calculated correlation matrix; a spectrum calculating means which calculates the spectrum based on the calculated weight matrix and a vector indicating directivity of the antenna; a spectrum peak detecting means which detects a direction with a peak value with the use of the calculated spectrum result; and an arrival direction calculating means which estimates an arrival direction of the signals based on spectrum results in the direction detected by the spectrum peak detecting means and peripheral directions thereof.

7. The arrival direction estimation apparatus according to claim 6 , wherein the spectrum calculating means calculates the spectrum by using a multiplication result of elements of the vectors indicating directivity of the antenna.

8. An arrival direction estimation apparatus comprising: an antenna in which a plurality of antenna elements are symmetrically arranged centering on a given reference position or a reference line and which receives signals by the plurality of antenna elements; a complex digital signal converting means which converts the signals received by each antenna element of the antenna to complex digital signals; a real number correlation matrix calculating means which calculates a real number correlation matrix expressing correlation among the plurality of antenna elements of the complex digital signals; a real number weight matrix calculating means which calculates a real number weight matrix used for calculating a spectrum based on the calculated real number correlation matrix; an inverse unitary converting means which provides the calculated real number weight matrix with inverse unitary conversion to calculate a complex weight matrix; a spectrum calculating means which provides the calculated complex weight matrix with Fast Fourier Transform to calculate the spectrum; a spectrum peak detecting means which detects a direction with a peak value with the use of the calculated spectrum result; and an arrival direction calculating means which estimates an arrival direction of the signals based on spectrum results at the direction detected by the spectrum peak detecting means and peripheral directions thereof.